• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.386-387
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• 2013

This paper provides a comparison of high power semiconductor devices in 5MW-class Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) wind turbines. High power semiconductor devices of IGBT module type, IGBT press-pack type, and IGCT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on neutral-point clamed 3-level back-to-back type voltage source converter supplied from grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through the loss analysis considering both conduction and switching losses under the given operating conditions of 5MW-class PMSG wind turbines, particularly for the application in offshore wind farms. The loss analysis is confirmed through PLECS simulations. The comparison result shows that IGBT press-pack type semiconductor device has the highest efficiency and IGCT has the lowest cost factor considering the necessary auxiliary components.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.263-269
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• 2018

In this study, a selective inverter operation between a 2-level voltage source converter (VSC) and a 3-level T-type VSC (3LT VSC) is proposed to improve the efficiency of a 3LT VSC. The 3LT VSC topology, except for its neutral-point switches, has similar operations as that of the 2-level VSC. If an operation mode is changed according to efficiency, the efficiency can be improved because efficiencies of each methods are depending on current and MI (Modulation Index). The proposed method calculates the power losses of the two topologies and operates as the having lower losses. To calculate the losses, the switching and conduction losses based on the operation mode of each topology were analyzed. The controller determined the operation mode of the 2- or 3-level VSC based on the power loss calculated during every cycle. The validity of the proposed control scheme was investigated through simulation and experiments. The waveform and average efficiency of each method were compared.

• Journal of the Korean Society of Combustion
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• v.18 no.2
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• pp.42-50
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• 2013

Linear stability analysis of radiating counterflow diffusion flames is numerically conducted to examine the instability characteristics of cellular patterns. Lewis number is assumed to be 0.5 to consider diffusional-thermal instability. Near kinetic limit extinction regime, growth rates of disturbances always have real eigen-values and neutral stability condition of planar disturbances perfectly falls into quasi-steady extinction. Cellular instability of disturbance with transverse direction occurs just before steady extinction. However, near radiative limit extinction regime, the eigenvalues are complex and pulsating instability of planar disturbances appears prior to steady extinction. Cellular instability occurs before the onset of planar pulsating instability, which means the extension of flammability.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.491-497
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• 2003

The use of both an Alpha Hydroxy Acid, Citric Acid, and a Skin Moisturizer, Glycereth-26, formulated into a hand dishwashing detergent have been shown to be synergistic in their effects on certain skin health parameters. Each ingredient was evaluated alone and together in a hand dishwashing detergent via a 9-week use test. Panelists washed dishes using the sponge method commonly used in Asian markets and a 1:7 dilution of the concentrated dish detergent. Panelist's hands were evaluated initially and at 3-week intervals for nine weeks. After nine weeks panelist's hands showed significant improvements in Moisture Absorption and Transepidermal Water Loss (TEWL). A synergistic effect on TEWL was found between the AHA and the Moisturizer. These effects, showing an improvement in the condition of the panelist's skin are impressive, particularly since they were observed from a dishwashing product that is highly diluted and at near neutral pH during the washing process.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.417-423
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• 2003

The use of both an Alpha Hydroxy Acid, Citric Acid, and a Skin Moisturizer, Glycereth-26, formulated into a hand dishwashing detergent have been shown to be synergistic in their effects on certain skin health parameters. Each ingredient was evaluated alone and together in a hand dishwashing detergent via a 9-week use test. Panelists washed dishes using the sponge method commonly used in Asian markets and a 1:7 dilution of the concentrated dish detergent. Panelist's hands were evaluated initially and at 3-week intervals for nine weeks. After nine weeks panelist's hands showed significant improvements in Moisture Absorption and Transepidermal Water Loss (TEWL). A synergistic effect on TEWL was found between the AHA and the Moisturizer. These effects, showing an improvement in the condition of the panelist's skin are impressive, particularly since they were observed from a dishwashing product that is highly diluted and at near neutral pH during the washing process.

• The Korean Journal of Community Living Science
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• v.21 no.1
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• pp.117-124
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• 2010

Recently, research on variables associated with hair styles are increasing with the spreading of total coordinated intention in the fields of clothing and cosmetology. In the present study, we focused on examining the skin temperature on the scalp(the vertex, temporal, and occiput), humidity on the occiput, skin temperatures (the forehead, back of ear, back of neck, upper back, abdomen, forearm, hand, thigh, calf, and foot), rectal temperature, total body mass loss by hair styles in a thermal neutral environment. Four young females participated as subjects. For a certain period, each subject had the five different hair styles in a random order: (1)Straight short hair(SS), (2)Perm waved short hair(PS), (3) Straight long hair(SL), (4)Perm waved long hair(PL), (5)Ponytail style(PT). Subjects wore briefs, bra, shirts with long sleeves, long legged training pants, and socks. The environmental variables of a climatic chamber were kept constant at $21{\pm}0.5^{\circ}C$ of air temperature and 55${\pm}$5%RH of air humidity. The results indicated the following: The skin temperature and humidity on the scalp did not show any significant differences among five different hair styles, but straight long hair style(SL)was the highest on the vertex, temporal, and occiput. The temporal skin temperature($29.8\sim30.8^{\circ}C$) was the highest, while the vertex skin temperature($28.7\sim30.1^{\circ}C$) was the lowest. Humidity on the occiput was the highest in the perm waved long hair style(PL). The back of ear skin temperature was significantly lower in the ponytail style(PT) than in the other four hair styles(p<.001). In the straight long hair style(SL), the skin temperature on the back of the neck and on the upper back were significantly higher than those of the other four hair styles(p<.01). Mean skin temperature and rectal temperature had no significant differences among hair styles. Total body mass was the highest in the perm waved long hair style(PL)(p<.05). We acquired fundamental data to enable the improvement of the current hair clinic system, wigs, functional hats, and helmets.

• Steel and Composite Structures
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• v.50 no.3
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• pp.299-318
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• 2024

The main objective of this paper is to compute the far-field acoustic radiation (sound radiation) of functionally graded plates (FGM) loaded by sinusoidally varying point load subjected to the arbitrary boundary condition is carried out. The governing differential equations for thin functionally graded plates (FGM) are derived using classical plate theory (CPT) and Rayleigh integral using the elemental radiator approach. Four cases, segregated on power-law index k=0,1,5,10, are studied. A novel approach is illustrated to compute sound fields of vibrating FGM plates using the physical neutral surface with an elemental radiator approach. The material properties of the FGM plate for all cases are calculated considering the power law indexes. An in-house MATLAB code is written to compute the natural frequencies, normal surface velocities, and sound radiation fields are analytically calculated using semi-analytical formulation. Ansys is used to validate the computed sound power level. The parametric effects of the power law index, modulus ratios, different constituent of FGM plates, boundary conditions, damping loss factor on the sound power level, and radiation efficiency is illustrated. This work is the benchmark approach that clearly explains how to calculate acoustic fields using a solid layered FGM model in ANSYS ACT. It shows that it is possible to asymptotically stabilize the structure by controlling the intermittent layers' stiffness. It is found that sound fields radiated by the elemental radiators approach in MATLAB, ANSYS and literatures are in good agreement. The main novelty of this research is that the FGM plate is analyzed in the low-frequency range, where the stiffness-controlled region governs the whole analysis. It is concluded that a clamped mono-ceramic FGM plate radiates a lesser sound power level and higher radiation efficiency than a mono-metallic or metal-rich FGM plate due to higher stiffness. It is found that change in damping loss factor does not affect the same constituents of FGM plates but has significant effects on the different constituents of FGM plates.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.179-187
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• 1998

A neutral particle energy analyzer, which has the carbon stripping foil and the $90^{\circ}$ cylindrical electrostatic deflection plate, was designed and constructed for measuring of ion temperature in plasma. The energy calibration and energy resolution were studied in detail for a hydrogen ion at the $0.5{\sim}3.0\;keV$ energy using a duoplasmatron ion source. An energy of hydrogen ion to the deflection plate voltage at the peak ion count rate could be fitted by the expression $E_{o}(keV)$=3.83V(kV). The measured energy resolution, which was about 2 % at the energy of 3.0 keV and 9 % at the energy of 0.5keV, was better for the increased hydrogen ion energy. For the charge exchanged hydrogen atom due to the carbon stripping foil, the energy calibration, energy loss and resolution were measured to the $0.5{\sim}2.0{\mu}g/cm^{2}$ thickness of the carbon stripping foil. An energy of the charge exchanged hydrogen atom as a function of the deflection plate voltage and carbon foil thickness could be fitted by the expression $E_{o}(keV)=(0.53d+4.4){\cdot}V(kV)$. The energy loss was $0.23{\sim}0.89\;keV $ to the $0.5{\sim}2.0{\mu}g/cm^{2}$ carbon foil thickness and the $0.5{\sim}3.0\;keV$ energy of the incident neutral hydrogen atom, it could be fitted by the expression ${\Delta}E=(0.12d+0.27){\cdot}{E_{o}}^{1/2}(keV)$. The measured energy resolution for the neutral hydrogen atom, which was between 7 % and 35 % in this experiment region, was increased for the increasing neutral hydrogen atom energy and the decreasing carbon stripping foil thickness.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.9
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• pp.71-80
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• 2015

This paper proposes a convenient thermal modeling method for loss distribution control method of 3-level Active NPC(Neutral Point Clamped) inverter. In the drawback of conventional 3-level NPC, the generated losses can occur unbalance in each switching device, as a result, thermal utilization of designed system has been decreased. In order to compensate unbalanced losses, Active NPC inverter performed loss balancing control with thermal modeling during operation of each switching device. Therefore, this paper deals with a convenient thermal modeling method based on newton's law of cooling rather than conventional thermal modeling method. Both simulation and experimental results based on 10kW 3-level Active NPC inverter confirm the validity of the analysis performed in the study.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.61-66
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• 2012

Conventional method to transform vehicle driving condition to engine operation mode is to use vehicle road load under neutral gear and mechanical efficiency of drivetrain. But this method requires additional measurement of efficiency of drivetrain on a test rig. And this measurement is normally done at fixed speed and thus estimated accuracy of engine operation mode is not considered to be high enough. This study suggests new method to calculate engine operation mode for prescribed driving mode such as NEDC using vehicle coastdown test under gear engaged condition without measurement of mechanical efficiency of drivetrain. Coastdown test was done under neutral and gear engaged condition for comparison and also trial to extract mechanical loss of drivetrain was carried out. Calculated engine torque by conventional and newly suggested method was compared with actually measured torque of a vehicle on a chassis dynamometer during NEDC. Newly suggested method showed slightly higher accuracy of accumulated brake work during NEDC.